OUR best shot at finding life beyond Earth may lie in the icy moons of the outer solar system - particularly Titan and Enceladus, which orbit Saturn, and Jupiter's moon Europa. We think they all have vast liquid water oceans beneath their frozen outer shells thanks to their highly elliptical orbits, which create such intense tidal forces that they are warmed from the inside out. Europa's ocean is thought to be much deeper than those on Earth, but with a similar chemical balance. Enceladus, meanwhile, spews geysers into its atmosphere that contain at least some of the ingredients life requires. If life exists in these places, Kevin Hand wants to find it. As director of the ocean worlds lab at NASA's Jet Propulsion Laboratory in California, he is a leading expert on the potential habitability of these far-flung moons and a key player in the design of missions to explore them. In his new book-Alien Oceans: The search for life in the depths of space (Princeton University Press), Hand describes what he has learned from his voyages to the bottom of Earth's oceans and how that informs his plans to send a life-seeking lander to Europa.
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